Criminal (and some civil) investigations often require a search by law enforcement authorities. Most nations recognize that permitting a search of individuals or property without procedural guardrails can be problematic. In response, they have developed legal principles that balance the inviolability of privacy interests and the need for effective public security. A search warrant is a legal authorization to conduct a search based upon credible information connecting the subject of the search to a crime. Many countries require a judge or magistrate to review law enforcement search requests; others delegate warrant authority to the prosecutor. In some nations warrant requirements are limited to very narrow circumstances or do not exist at all. The scope and particulars of a country’s search warrant process reflect the contours of its polity, criminal justice system, and social norms.
This piece provides an overview of search warrant rules adopted by different criminal justice systems. The admissibility of evidence seized in violation of warrant requirements will be discussed in a separate post.
What is a Search Warrant?
A search warrant is a document signed by a neutral authority permitting law enforcement to search a person or property for evidence of a crime. A warrant requirement may be included in a nation’s constitution, detailed in the criminal procedure law, or made obligatory by virtue of being a signatory to an international human rights instrument. A warrant application must be based on a credible, substantiated belief that a crime was committed (probable cause) and that evidence of illegality will be found. In most countries, the factual basis for a warrant must be truthful and specific, setting forth particularized information about the location to be searched and the evidence to be seized. Warrants must also be timely and executed in a reasonable manner. For example, the warrant may provide a detailed time period for its execution.
Constitutional protections and related code provisions addressing privacy interests and government authority may be general and require judicial analysis and elaboration through court judgments.
History
The Code of Hammurabi, one of the earliest recorded legal codes, does not explicitly mention searches, but it does emphasize fairness and due process, values that underlie the rationale for warrants. The genesis of the modern search warrant has been traced to the American colonial era when residents objected to searches conducted by British officials. Writs of assistance, first used by King Henry VIII in the mid-16th century, gave British officers broad authority to search homes and businesses and seize property. Recognizing this expansive authority was vulnerable to abuse, parliament limited the use of the writs in England, but they were broadly employed by customs officials in the colonies. In 1761, the writ of assistance was challenged in court by Boston attorney James Otis who famously argued “a man’s home is his castle.” This principle was later enshrined in the Fourth Amendment of the United States Constitution, a provision that protects individuals from unreasonable searches and seizures by the government.
Authority to Issue: Prosecutor or Judge?
In some countries, including the United States, searches can only be authorized by a judge. Prosecutors are not considered sufficiently neutral to make the probable cause determination. By contrast, in many other countries, including Germany, although the prosecutor is part of the executive branch, it is deemed have a quasi-judicial role in the fact-finding process. Prosecutors are considered “organs of justice” and duty-bound to search for and consider inculpatory and exculpatory evidence.
Implementation
The warrant application can be made by submitting a sworn, written affidavit to a judge or prosecutor, in person. Some countries now authorize this process to take place over the phone, video, or electronically.
The scope of a permissible search is typically limited, whether by criminal procedure law or judicial decree. For example, the search of a person is restricted to their immediate area and effects, pockets, and items within their reach such as bags and backpacks. A warrant to search a home or business usually must set forth details specifying the rooms and items (computers, clothes etc.) to be searched. The authority to search electronics (smartphones, computers, servers) may require an additional warrant.
International Standards
Although a search warrant is not mandated by international law, international law instruments and norms affirm the right to privacy. Article 17 of the International Covenant on Civil and Political Rights states: “No one shall be subjected to arbitrary or unlawful interference with his privacy, family, home and correspondence …” The European Convention on Human Rights (Article 8) similarly recognizes an individual’s right to privacy in their home, family life, and correspondence and any governmental interference with this right must be carried out “in accordance with the law and [as] is necessary” to prevent crime and protect the health, rights, and freedoms of others.
Exceptions
Many searches by law enforcement are warrantless, falling into one of the many legal exceptions such as consent, search incident to arrest, and exigency (imminent danger or the destruction of property). Police authorities in most countries may conduct a warrantless search when pursuing a fleeing suspect into a home or building and during administrative inspections of buildings. Most countries that require a search warrant have an automobile exception based on the mobility of vehicles. For example, in Kenya, Singapore, Spain, and the United States, police may search a vehicle if there is probable cause to believe that it contains evidence or contraband; in Canada a vehicle can be searched if there is a risk that the evidence will be moved or lost.
Verification
Some countries enable the subject of a search warrant to petition for verification of the facts used to obtain a warrant. In Poland and Germany, the lawfulness and necessity of a warrant can be contested before trial, whether or not items were seized. By contrast, in the United States, the legality of a search is challenged in pretrial hearings to exclude evidence. In Italy, a defendant can request a judgment for verification only in cases where items were seized. This limitation was criticized by the European Court of Human Rights in a 2018 judgment, Brazzi v. Italy. In that case, the prosecution executed a search during a preliminary criminal investigation with no judicial review before or after the search was executed. The Court ruled that Italy’s law (limiting judicial review to searches where evidence was seized) is contrary to Article 8 § 2 of the Convention and violated Mr. Brazzi’s “right to respect for his home.”
No-Knock Warrants
According to United States Supreme Court precedent, the Fourth Amendment incorporates the common law rule that before entering a building to execute a search warrant, police must knock on the door and announce their identity and purpose. In the 1970’s, law enforcement authorities argued that this notice enabled the destruction of evidence, flight, and posed a danger to officers; a remedy was implemented: quick-knock (knock and wait 15-20 seconds before entry) and no-knock warrants. In the 1980’s and 90’s, their use became more widespread as part of the ‘war on drugs.’ Although the Supreme Court approved no-knock warrants in a 1997 case, it held that judges must examine the facts of each case to assess whether their use was justified. There must be a reasonable suspicion that “knocking and announcing their presence, under the particular circumstances, would be dangerous or futile, or that it would inhibit the effective investigation of the crime.”
Critics of no-knock warrants in the United States argue that they are requested and issued with increasing frequency and often result in greater risk of injury to both suspects and law enforcement officers. Well publicized cases of no-knock warrants resulting in police injuring innocent people led to campaigns to eliminate their use. Twenty-nine states and 21 cities have limited the application of no-knock warrants, and four states have banned them entirely. In Canada, police, not the courts, have the authority to determine when a no-knock entry is permissible. A judicially approved warrant is not required. Some estimates indicate that these ‘dynamic entries’ are used in 90% of drug raids in Ontario. This practice has been criticized as a violation of Canada’s Charter of Rights and Freedoms.
Country Examples
Article 8 of Canada’s Charter of Rights and Freedoms guarantees everyone the right “to be secure against unreasonable search or seizure.” Canada’s criminal code sets forth the requirements for seeking a warrant. Law enforcement must submit a warrant application to a judge, under oath, that sets forth reasonable grounds to believe a crime has been committed, evidence related to the crime is located in the area to be searched, or items that will be used in the commission of a crime will be found there. Section 487 of the Criminal Code also addresses the search of computers and copy equipment. If the time for a search is not specified in the warrant, Canadian law implies a requirement that the search be executed within a reasonable time from when it was issued. Although under Canadian law warrantless searches are presumed unreasonable, there are exceptions including exigency, search incident to arrest, items in plain view, and legislation authorizing a warrantless search. In addition, the presumption of unreasonableness can be rebutted by a showing based upon subjective and objective evidence that the search was reasonable.
The authority to conduct a search in Colombia is regulated by the constitution and the criminal code. Warrants are issued by a judge, based upon a showing of probable cause by the prosecutor. Warrants are executed by an investigator (a member of the judicial police). As in most other countries, there are broad exceptions to the warrant requirement including exigent circumstances and consent.
France has different types of criminal investigations with different principal actors and procedural rules. Most minor criminal offenses are investigated by police authorities under the supervision of a prosecutor. When a search is conducted, the owner of the premises or another civilian must be present and consent to the search. For criminal charges punishable by at least three years, the prosecutor may issue a search warrant if there is a “plausible reason” to believe a crime has been committed or attempted by the subject of the search. For more serious crimes, the Investigating Magistrate leads the investigation with the assistance of judicial police. Warrant applications for these cases may be reviewed by a Liberties and Custody Judge. If the subject of the search warrant is not present when the warrant is executed, the warrant remains valid for the duration of the investigation or until it is revoked by the investigating judge. In response to the 2015 terror attack in Paris, parliament passed legislation in 2017 expanding police authority to conduct warrantless searches in terrorism cases.
The constitution of India provides for a right to life and personal liberty. This has been interpreted by the Supreme Court to afford protections against unreasonable searches. A warrant is not required for all searches. The Code of Criminal Procedure sets forth specific rules governing the search process. Search warrants may be issued only by a magistrate and upon a finding of reasonable suspicion or credible evidence that an offense has occurred or indicia of criminality will be found. The warrant must specify the place to be searched and the items sought. In some types of cases, the search must be conducted in the presence of a witness (panchas) and detailed records of the search maintained. In lieu of a warrant, a search may take place in the presence of a magistrate. Warrantless searches are also permitted if the police have reasonable grounds to believe that delay will impair the investigation or there is a risk that evidence will be concealed or destroyed. There are special laws in India that dispense with the warrant requirement including the Narcotic Drugs and Psychotropic Substances Act, the Unlawful Activities (Prevention) Act, and the Prevention of Terrorism Act.
Italy’s Criminal Procedure Code provides that a “judicial authority” has the power to conduct or order a search. This term refers to judges and prosecutors. In practice, warrants are typically reviewed and issued by prosecutors. Italian law also recognizes exceptions to the search warrant requirement, such as exigent circumstances and instances when police have reasonable grounds to believe that an individual is concealing relevant evidence that can be lost or destroyed. However, after conducting a warrantless search, the police must inform the prosecutor who then has 48 hours to confirm the appropriateness of the search.
Japan’s constitution includes a requirement that any search of a person’s home, papers, and effects requires a warrant “particularly describing the place to be searched and things to be seized” and warrant applications must be reviewed “by a competent judicial officer.” Rules for executing warrants are described in the Code of Criminal Procedure. A search warrant must include the name of the accused, items to be seized, place searched, and a period for conducting the search. Judges review warrant applications. Although Japanese law references ‘reasonable suspicion,’ the term as applied in the context of a search warrant is not defined. Once a warrant is approved, the search is executed by the public prosecutor’s assistant or a judicial police officer. In May 2025, Japan’s parliament reviewed a bill permitting an electronic warrant application process. Currently investigative authorities must go to court to obtain a warrant.
In Mexico, the National Code of Criminal Procedure sets forth the requirements for a search warrant, drawing upon guarantees in the constitution and international treaties to which Mexico is a party. Search warrants in Mexico are requested by a prosecutor and issued by a Juez de Control. Warrants are used to inspect private property in order to find a person, evidence, or other instruments related to the commission or a crime; they must specify the area and items to be searched. Warrants can be approved electronically or in person and must be executed within three days.
Section 21 of the 1990 New Zealand Bill of Rights Act states: “Everyone has the right to be secure against unreasonable search or seizure, whether of the person, property, or correspondence or otherwise.” This guarantee was codified in the Search and Surveillance Act of 2012. In New Zealand, a judge reviews warrant applications submitted by a constable, either in person or electronically. The warrant application must include reasonable grounds to suspect that the specified offense was committed, is being committed, or will be committed and that the search will yield evidence related to the offense described in the warrant. New Zealand law includes a limit on how many times a warrant can be used. Warrants are typically valid for 14 days after issue.
Under Poland’s Code of Criminal Procedure, a search warrant is required for most criminal investigations unless exigent circumstances pose an immediate need to detain an individual or seize evidence; this includes concerns that evidence will be lost, destroyed or tampered with. Prosecutors issue search warrants and may conduct the search or authorize the police or a law enforcement agency to do so. Judges review the validity of the search at trial. For searches conducted without a warrant, police are required to immediately seek confirmation of the warrantless search from a prosecutor. If a search is not confirmed within seven days, the property seized must be returned to the owner. The subject of a search may seek an interlocutory appeal challenging its legality.
In 2021, Russia passed new legislation authorizing police to search homes and vehicles without a warrant. This broad authority extends to the homes of those who are not suspected of committing a crime. Similarly, police may conduct a warrantless search of individuals who are suspected of possessing contraband.
South Africa’s constitution provides for a right to privacy that specifically incorporates “the right not to have their home searched.” However, search warrants are permitted and rules governing their execution are set forth in the criminal procedure law. A warrant may be issued when there are reasonable grounds to believe that the place or items to be searched are connected to a crime, will provide evidence of criminal conduct, or are intended to be used in the commission of a crime. These factual allegations must be signed under oath and reviewed by a judicial officer. If one is not available, the police may seek a warrant from a justice of the peace; justices of the peace are either senior prosecutors or commissioned police officers. In practice, many warrants in South Africa are issued by justices of the peace. This has raised concerns that warrant applications may not always be subject to sufficiently independent and objective review.
The Fourth Amendment of the United States Constitution guarantees the “right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures” and provides that “no Warrants shall issue, but upon probable cause, supported by Oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized.” Search warrant procedures are included in the rules of procedure for federal and state courts. In the federal courts, a magistrate judge may issue a warrant to search for evidence of criminal conduct. The warrant application must include a sworn statement or testimony setting forth facts supporting probable cause to believe a crime has been committed, indicating the person, property, and area to be searched, and the items to be seized. The warrant must be executed during the day unless there is good cause to allow otherwise. Police officers must execute the search within 14 days of the warrant being issued and keep an inventory of items seized. Most jurisdictions in the United States allow for electronic warrant applications. As is the case in most other countries, a significant percentage of the searches conducted by police in the United States are warrantless, falling within one of the many exceptions to the warrant requirement. Under US law, if police obtain a warrant that is later found to be invalid but relied upon it “in good faith,” the evidence seized is deemed admissible.
Geofence Warrants
The geofence warrant has been called a ‘reverse warrant.’ Rather than a request to search a particular place or person suspected of a crime, a geofence warrant seeks to identify suspects when none are known, gathering information that may be relevant to an investigation. A geofence warrant does not require the use of detailed information or a finding of probable cause. It is used by law enforcement to compel technology companies to gather information about who was within a particular area (a geofence) during a specified time period. This information – the individual’s location history – is culled from the interaction of a user’s device with GPS, Bluetooth beacons, cell towers, and Wi-Fi networks.
Only United States law enforcement currently uses geofence warrants and their legality has been challenged throughout the country. Does a geofence warrant constitute a search under the Fourth Amendment? If so, does a warrant provide sufficient protection under the Fourth Amendment given the intrusiveness of the technology? Courts in the United States are divided. In December 2023, Google announced that location data will only be accessible from a user’s device and will not be stored in the cloud. This change has made it much more difficult, if not impossible, to provide the information requested in geofence warrants.